The invention relates generally to systems which generate images during medical and surgical procedures, and in particular, a system for generating images during medical and surgical procedures based on a scan taken prior to the procedure.
Image guided medical and surgical procedures comprise a technology by which images, obtained either pre-procedurally or intra-procedurally (i.e., prior to or during a medical or surgical procedure), are used to guide a doctor during the procedure. The recent increase in interest in this field is a direct result of the recent advances in imaging technology, especially in devices using computers to generate three dimensional images of parts of the body, such as computed tomography (CT) or magnetic resonance imaging (MRI).
The majority of the advances in imaging involve devices which tend to be large, encircle the body part being imaged, and are expensive. Although the images produced by these devices depict the body part under investigation with high resolution and good spatial fidelity, their cost usually precludes the dedication of a unit to the performance of procedures. Therefore, image guided surgery is usually performed using images taken preoperatively.
The reliance upon preoperative images has focused image guidance largely to the cranium. The skull, by encasing the brain, serves as a vessel which inhibits changes in anatomy between imaging and surgery. The skull also provides a relatively easy point of reference to which a localization system may be attached so that registration of pre-procedural images to the procedural work space can be done simply at the beginning of the procedure. Registration is defined as the process of relating pre-procedural images of anatomy to the surgical or medical position of the corresponding anatomy. For example, see Ser. No. 07/909,097, now U.S. Pat. No. 5,383,454, the entire disclosure of which is incorporated herein by reference.
This situation of rigid fixation and absence of anatomical movement between imaging and surgery is unique to the skull and intracranial contents and permits a one-to-one registration process as shown in FIG. 1. The position during a medical procedure or surgery is in registration with the pre-procedural image data set because of the absence of anatomical movement from the time of the scan until the time of the procedure. In almost every other part of the body there is ample opportunity for movement which degrades the fidelity of the pre-procedural images in depicting the intra-procedural anatomy. Therefore, additional innovations are needed to bring image guidance to the rest of the body beyond the cranium.
The accuracy of image guided surgery is based on the identification of structures within the body that do not change shape, do not compress, nor deform between the process of imaging and surgery. Such structures are termed xe2x80x9crigid bodies,xe2x80x9d and the bones of the skeleton satisfy this definition for a rigid body. Bones are commonly a target for medical or surgical procedures either for repair, fusion, or biopsy. Therefore, a technique is needed whereby registration can be performed between the bones or bone fragments (skeletal elements) as depicted pre-procedurally on scans and the position of these same skeletal elements as detected intra-procedurally. This technique must take into account that movement can occur between portions of the skeleton which are not rigidly joined, such as bones connected by a joint, or fragments of a broken bone.
It is an object of this invention to provide a system which allows registration between multiple skeletal elements depicted in pre-procedural images and detected during surgery.
It is a further object of this invention to provide a system which can localize multiple rigid bodies that move with respect to each other between imaging and a procedure and provide a display during the procedure of the bodies in their displaced positions.
It is another object of this invention to provide a system for use during a medical or surgical procedure on the body, the system generating a display representing the position of two or more body elements during the procedure based on an image data set generated by a scanner prior to the procedure.
It is another object of this invention to provide a system for use during a medical or surgical procedure on a body which modifies the image data set according to the identified relative position of each of the elements during the procedure.
It is another object of this invention to provide a system which generates a display representative of the position of a medical or surgical instrument during a procedure in relation to body elements.
It is a further object of this invention to provide a system for use during image guided medical and surgical procedures which is easily employed by the doctor or surgeon conducting the procedure.
It is another object of this invention to provide a system which determines the relative position of body elements based on the contour of the body elements which, in some cases, avoids the need for exposing the body elements.
It is still another object of this invention to provide a system which employs the projected fluoroscopic images of body elements to determine their relative position.
It is yet a further object of this invention to describe a surgical or medical procedure which employs a display representing the position of body elements during the procedure based on an image data set of the body elements generated prior to the procedure.
It is a further object of this invention to provide a system and method for medical or surgical procedures which allows repositioning of body elements during the procedure and still permits the generation of a display showing the relative position of the body elements.
Other objects and features will be in part apparent and in part pointed out hereinafter.
The invention comprises a system for use during a medical or surgical procedure on a body. The system generates a display representing the position of two or more body elements during the procedure based on an image data set generated by a scanner prior to the procedure, the image data set having reference points for each of the body elements. The reference points of a particular body element have a fixed spatial relation to the particular body element. The system includes means for identifying, during the procedure, the relative position of each of the reference points of each of the body elements to be displayed. The system also includes a processor modifying the image data set according to the identified relative position of each of the reference points during the procedure, as identified by the identifying means. The processor generates a displaced image data set representing the position of the body elements during the procedure. The system also includes a display utilizing the displaced image data set generated by the processor and illustrating the relative position of the body elements during the procedure.
The invention also comprises a method for use during a procedure. The method generates a display representing the position of two or more body elements during the procedure based on an image data set generated prior to the procedure, which image data set has reference points for each of the body elements. The method comprises the steps of:
identifying, during the procedure, the relative position of each of the reference points of each of the body elements to be displayed;
modifying the image data set according to the identified relative position of each of the reference points during the procedure in order to generate a displaced image data set representing the position of the body elements during the procedure; and
generating a display based on the displaced image data set illustrating the relative position of the body elements during the procedure.
The invention also comprises a method for use with two or more body elements which each have reference points. The method comprises the steps of:
prior to a procedure:
placing the body elements in a frame to fix their relative position; and
scanning the fixed body elements; and
during the procedure:
placing the body elements in the frame so that the body elements have the same relative position as their position during scanning;
determining the position of reference points on the body elements relative to reference means;
determining the position of a medical or surgical instrument relative to the reference means;
determining the position of the medical or surgical instrument relative to the body elements; and
generating a display based on the pre-procedural scanning illustrating the determined position of the medical or surgical instrument relative to the body elements.